Support for an a i brj-catalyzed reaction



Feb. 4, 1964 M. F. MCDONALD, sR.. ETAL 3,120,494

CATALYST COMPOSITION AND PROCESS FOR IMPREGNATING A SUPPORT FOR AN AIBr CATALYZED REACTION Filed Sept. 5, 1959 3 Sheets-Sheet l REACTOR 24 ;-p l I I IS I4 FIGURE I Michael Francis McDonold,'Sr. Eor l Joseph Estopinul, JR INVENTORS BY Wu m PATENT ATTORNEY Feb. 4, 1964 M. F. MCDONALD, sR.. ETAL 3,120,494

CATALYST COMPOSITION AND PROCESS FOR IMPREGNATING A SUPPORT FOR AN AI Br -CATALYZED REACTION Filed Sept. 3, 1959 3 Sheets-Sheet 2 $50: 22; 8 me 9 mm 8 mm ow m. o m 0 m T N w m O- V r p m w r. O J M n 1 1 m m ON% C 5:3 9 mzz. 20.2522 o M m 5: 0 5 no-3 1.1- N .w II..N S m :lllllillllli n m h lill 3M m m a o I. .m J .w M M E 3 5. s. 5 m

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PATENT ATTORNEY Feb. 4, 1964 F. M DONALD, SR., ETAL CATALYST COMPOSITION AND 3,120,494 PROCESS FOR IMPREGNATING A SUPPORT FOR AN AlBq-CATALYZED REACTION Filed Sept. 5, 1959 5 Sheets-Sheet 5 INVENTORS \/J. r-Q

PATENT ATTORNEY United States Patent 3,120,494 CATALYST CGMPOSITION AND PROCESS FOR IMPREGNATING A SUPPGRT FUR AN AlBr CATALYZED REACTION Michael Francis McDonald, Sr. and Earl Joseph Estopinal, Jr., Baton Rouge, La., assignors to R550 Research and Engineering Company, a corporation of Delaware Filed Sept. 3, 1959, Ser. No. 837,845 8 Claims. (Cl. 252-442) This invention concerns improvements in the catalytic treatment of paraflin hydrocarbons. More particularly, the invention relates to improvements in the liquid phase conversion of normal or slightly branched chain hydrocarbons to commercially valuable, more highly branched isomers, employing aluminum bromide as the catalyst. Still more particularly, the present invention relates to improvements in the starting up of a reactor for carrying out the process on a commercial scale.

It is well lmown that the more highly branched isomers of the parafiinic hydrocarbons occurring in petroleum gasoline fractions are more valuable than the corresponding slightly branched or straight chain hydrocarbons because of their higher octane ratings. The demand for motor fuels of greater octane number has increased markedly as the automotive industry has provided gasoline engines with increasingly higher compression ratios to attain greater efiiciency. Oneof the economically important ways in which the increased demands for high octane fuels can be met is through the isomerization of the light naphtha components of such fuels.

It may be generally stated that the isoparaiiinic and branched chain parafiin hydrocarbons are of greater commercial value to the petroleum industry than the corresponding straight chain hydrocarbons. Thus, for example, 2,2-dimethylbutane has a higher octane rating than the isomeric normal hexane. Isobutane is more valuable than normal butane since the former can be used as the basis for the preparation of 8-carbon-atom branched chain hydrocarbons by alkylation with butylene.

The isomerization of normal paraflin hydrocarbons of from 4 to 7 carbon atoms into the corresponding branched chain homologs is well known. For effecting the isomerization, it is customary to employ certain metal halides, particularly aluminum chloride or aluminum bromide, in conjunction with certain promoters, such as hydrogen chloride, hydrogen bromide or boron fluoride. Insofar as the isomerization of light naphthas is concerned, the lowerthe temperature of isomerization, within limits, the more favorable is the equilibrium for converting straight chain paraffin hydrocarbons into isomers of high octane rating. Aluminum bromide has been found to be more active than aluminum chloride at lower isomerization temperatures, e.g., in the range of about 50 to about 120 F.

Aluminum bromide is also known to be an active catalyst for the alkylation of isoparaffinic hydrocarbons with olefinic hydrocarbons to produce branched chain hydrocarbons that are useful motor fuel components. The same catalyst, with suitable promoters, can be employed to eifect the liquid phase reaction of paraffin hydrocarbons of from 6 to 18 carbon atoms with isobutane or isopentane at temperatures of about 30 F. to about 120 F. to give products predominating in C to C branched chain hydrocarbons of high octane rating; in a process involving simultaneous cracking, isomerization and alkylation reactions.

One disadvantage in the use of aluminum bromide in reactions of the types outlined above is that it is appreciably soluble not only in the products of those reactions, but also in the starting materials. Because of this, practical means must be available not only for recovering the aluminum bromide from the reaction products so that it can be reused in the reaction, but also means must be taken to maintain catalyst in the active state in the reactor at all times. This is particularly difficult, for reasons set forth below, during the start-up of the operation.

A peculiarity of the aluminum bromide catalyzed hydrocarbon isomerization reaction is the fact that an activator, usually an oxygen containing material must be present to cause the reaction to proceed. Without them, the reaction will not go. These activators may be solid supports, such as bauxite, alumina, molybdena, silica gel, or similar materials; likewise, many liquid oxygen containing compositions, such as alcohols, ethers, organic and inorganic acids, carboxyl compounds and the like, have been found to a greater or less extent to function as activators. These activators probably form molecular complexes with the AlBr or its dimer, Al Br and it is the complex that actually functions as the catalytic agent.

A still further peculiarity about the AlBr catalyzed liquid phase hydrocarbon reaction systems is the fact that the catalyst must be present in two phases or species, namely AlBr associated with the activator or support, this forming a solid phase when a solid support is employed, and AlBr or Al Br dissolved in the reactant hydrocarbon. Again, it has been found that supported AlBr will not catalyze the liquid phase isomerization or isoparaflin alkylation process in the absence of dissolved AlBr Furthermore, after a support has become saturated, as with to of its weight of AlBr it will not isomerize hydrocarbons if free AlBris cut out of the feed. Normally, a catalyst support, such as Porocel,

which is a calcined bauxite, adsorbs about 30 to 70% by weight of AlBr from the solution. This means when starting up a commercial isomerization reactor, the reactor support, such as Porocel, alumina, molybdena and the like, must have 30 to 70% by weight of AlBr adsorbed before catalyst activity is stabilized.

The efliciency and technique of adsorbing this AlBr on a commercial reactor bed is extremely important from an economic standpoint. Thus, a 20,000 bd./d. isomerization unit with a design feed rate of 0.1 to 0.2 v./v./hr. will require from $300,000 to $800,000 worth of AlBr deposited on the reactor bed. Even when catalyst re-' cycle is employed, the maximum feed rate is about 0.6

to 0.8 v./v./hr., and AlBr cost would then be between $50,000 and $200,000.

It is an important object of the present invention to in a minimum period of time and with a maximum degree of effectiveness.

Other and further objects and advantages of the present invention will be more clear hereinafter.

In accordance with the present invention it has been found that the highest rates of AlBr adsorption (w. AlBr /hr./w. support) are obtained during start-up by having a feed composition of 2 to 20 wt. percent AlBr and 5 to 20 wt. percent HBr (based on total feed) and operating at 0.5 to 10 v./v./hr. Recycling the hydrocarbon feed stream, composed of isobutane and/ or naphthenes, both of which components are reactants in the isomerization process, and the dissolved AlBr and HBr across the reactor beds at the described v./v./hr. is critical to insure maximum utilization of feed additives. Both the isobutane and the naphthenes, i.e., methylcyclopentane, cyclohexane and methylcyclohexane, are cracking inhibitors and prevent catalyst degradation and fouling. Furthermore, to provide maximum efiiciencies, recycle conditions include liquid feed rates (AlBr dissolved in naphthenes and/or i-C of 0.5 to 10 v./v./hr., an AlBr concentration of 2 to 20 wt. percent based on feed, and a 5 to 20 wt. percent HBr concentration, based on feed. HBr serves not only to promote the isomerization reaction but also to stabilize the AlBr and aids in keeping it in solution. At the start-up, of course, the reactor is packed with the fresh activator, such as Porocel, alumina and the like.

The process of the present invention may be illustrated diagrammatically in FIGURE 1 of the accompanying drawings, wherein 2 represents an isomerization reactor during the start-up stage. This reactor may be packed with the activators previously mentioned. In order to deposit the desired quantity of AlBr on this activator bed, a stream of AlBr dissolved in naphthenes or isobutane, or in a mixture of both, is admitted through lines 24 and 12 into reactor 2. As indicated previously, the AlBr concentration is 2 to 20% by weight; and the solution is circulated through the reactor and the pump-around system by means of pump 6 until the reactor support carries 30 to 70 wt. percent AlBr Further admitted through lines 24 and 12 is 5 to 20% by weight of HBr, based on feed. Preferably the temperature within reactor 2 is about 60 to 150 F., and a pressure of to 150 p.s.i.g. is maintained. The feed rate must be maintained at least at 0.5 v./v./hr. for high efiiciency.

As shown in FIGURE 3 the relative adsorption rates are for the most part constant after 0.5 v./ v./ hr. Operating at rates less than 0.5 v./v./hr. would greatly increase the time necessary to saturate the support by limiting the amount of AlBr in contact with the support. There is no advantage for operation above 3 v./v./hr.

An excellent method of providing AlBr in a highly active form for this process is to synthesize it in situ. For this purpose, a portion of the stream from pump 6, comprising isobutane and/or naphthenes as well as HBr, is passed over a bed of aluminum ribbon or turnings or the like and AlBr in high purity is withdrawn in solution from zone 16 through line 18.

When sufficient AlBr is built up Within the reactor 2, valve 22 is closed, valve opened, and the system is now in readiness for the isomerization reaction proper. The latter, not being a part of the present invention, is not here illustrated, but it includes passage of a C -C normal hydrocarbon stream to reactor 2 and passage of isomerization product through line 34 to a conventional recovery system.

The critical nature of the variables that must be maintained to obtain saturation of the support in a short time is clearly shown in the curves in FIGURES 2 and 3.

FIGURE 2 shows that saturation of the support is achieved in a far shorter period of time at the higher HBr concentration levels than at the lower. FIGURE 3 indicates the upper limit of AlBr concentration and space velocity, above which no advantages are realized.

That it would be economically undesirable to employ a once-through operation for saturating the support is shown in Table I. The last column shows the amount of AlBr which passes out of the reactor with the etlluent. Thus if the total AlBr adsorbed in a commercial unit costs about $500,000, then operation 1 would lose $43,000 during the start-up; 2 would lose $780,000; and operation 3 would lose $294,000. This is calculated from the equation:

500 000 lost= 0 1 -percent AlBIg lost $0000 0 Table I ONCE-THROUGH AlBra ADSORPTION CONDITIONS Allin Lost,

Percent on Total Operation All'ln, HB Alllr; V./V./IIr. Wt. Wt. Temp., Fed to Percent Percent F. Reactor in Feed in Feed What is claimed is:

1. A process for impregnating a support for an AlBI'gcatalyzed reaction which comprises passing to an oxide support a hydrocarbon solution containing from 2 to 20% by weight of AlBr at a rate of 0.5 to 10 v./v./hr., further passing to said support 5 to 20 weight percent of HBr, based on hydrocarbon, and recycling said product until said support is saturated with aluminum bromide.

2. The process of claim 1 wherein said support is calcined bauxite.

3. The process of claim 1 wherein said support is alumina.

4. The process of claim 1 wherein said hydrocarbon is isobutane.

5. The process of claim 1 wherein said hydrocarbon comprises naphthenic hydrocarbon compounds.

6. The process of claim 1 wherein adsorption conditions include temperatures of 60 to F. and pressures of from 10 to 150 p.s.i.g.

7. An improved process for saturating an oxide support with AlBr which comprises recycling to said bed a 2 to 4% by weight solution of AlBr in a hydrocarbon selected from the class consisting of isobutane and naphthenes, further maintaining on said bed an HBr concentration of about 8 to 10% by weight of hydrocarbon, and maintaining a recycle rate of about 0.5 to 3 v./v./hr.

8. The process of claim 1 wherein at least a portion of said recycle stream is passed through a bed of aluminum to synthesize further amounts of AlBr References Cited in the file of this patent UNITED STATES PATENTS 2,265,548 Schuit Dec. 9, 1941 2,410,894 Montgomery Nov. 12, 1946 2,446,100 Oblad et al. July 27, 1948 2,971,037 Gilbert et al. Feb. 7, 1961 

1. A PROCESS FOR IMPREGNATING A SUPPORT FOR AN ALBR3CATALYZED REACTION WHICH COMPRISES PASSING TO AN OXIDE SUPPORT A HYDROCARBON SOLUTION CONTAINING FROM 2 TO 20% BY WEIGHT OF ALBR3 AT A RATE OF 0.5 TO 10 V./V./HR., FURTHER PASSING TO SAID SUPPORT 5 TO 20 WEIGHT PERCENT OF HBR, BASED ON HYDROCARBON, AND RECYCLING SAID PRODUCT UNTIL SAID SUPPORT IS SATURATED WITH ALUMINUM BROMIDE. 